PETALUMA (CBS SF) — A 30-year-old Santa Rosa woman was arrested Thursday in Petaluma after a police officer stopped her car for speeding and saw the woman’s unrestrained 4-month-old boy lying in the back seat, police reported.

The officer took Stacie Loomis into custody on suspicion of DUI and felony child endangerment following a traffic stop at about 11:23 p.m. Thursday on Petaluma Boulevard North, according to Petaluma police Lt. Tim Lyons.

Officer Corie Joerger, assigned to a K-9 unit, was in her police car when she noticed a Volvo Station Wagon traveling northbound on Petaluma Boulevard North at about 60 mph in a 45 mph zone, Lyons said.

Joerger pulled over the vehicle on Petaluma south of Industrial Avenue, contacted the driver and then noticed the infant boy lying face down in the back seat, police said.

The boy was not secured in either of two child car seats in the back of the vehicle, according to Lyons.

Loomis explained to the officer that she had just come from the boy’s father’s home and assumed the father had secured the child into a car seat before she drove away, Lyons said.

The woman appeared to be under the influence of alcohol and after an investigation, Joerger placed her under arrest and booked her into the Sonoma County Jail on suspicion of DUI and felony child endangerment.

Her bail was set at $50,000, Lyons said.

The boy was released into the care of his father, according to police.